The history of the developer circles is that we've been a bit rough with the language. (mount, finger, touch, zip, etc are perfectly acceptable things for linux commmands.. theres even a joke about it). Unsavory jokes in mailing list/code bases, etc. However, we've come upon a bunch of people who take the aggressively negative view on the words and interactions used and have taken it upon themselves to rename things and force changes. (Master/main, master/slave, whitelist/blacklist, [theres a whole list of these "undesirable" language things] etc ).
On top of that the CoC has implemented toxic positivity rules on projects. Implementers overlook the fact that they have been used as a weapon to be put in the project it's self. (There have been examples of racial, and gender based discrimination in the enforcement of the rules)
All of this brings in people who do not contribute in a UX, DX, engineering, management sort of way. Even when these things are abused/enforced poorly it still has a significant silencing effect and distancing effect from those who would be a positive contributor but is reluctant to participate.
I really don't buy the "some people just can't help being an asshole so having a rule against assholes is exclusionary." The most controversial CoC is by far the Contributor Covenant and rules are be kind and empathetic, show others respect, don't insult or demean others, don't be creepy or sexually harass others, don't doxx people, and behave like adults at work. Like the bar is so low.